Short wave signaling apparatus



1933 v J. o. WATKINS 3,920,223

SHORT WAVE SIGNALING APPARATUS Filed Sept. 16, 1930 INVENTGR JAMESQWATKINS ATTORN EY Patented Aug. 1,-

* UNITED" STA s PATENT OFFICE p v v. I 132-0223 W a V sHoR'r WAVESIGNALING APIARATUS 7' James 0. Watkins, 'San Francisco, Calif},assignor V to International Communications Laboratories, Inc., New York,N. Y., a Corporation of New York 3 10 Claims. (01. 250-20.)

This invention relates-to improvementsin signaling means; and moreparticularly to means for communication by radio upon so-called shortwaves or oscillationsof high frequency.

An object of the invention is to provide a device adapted for eithertransmitting or receiving means utilizing short-waves, to affordprotection against the troublesome effects of external electrostaticcapacity; thus maintaining the equipment in the desiredoperatingcondition.

A further object of the invention is to provide a simple, inexpensive,and novel appliance .for obviating the influence of the body of theoperator upon the apparatus in the circuits for signaling means of thistype. In signaling on short waves, this body-capacity effect is a .veryserious adverse factor and, if not counteracted, will alter toa-considerable extent the wave length for which adjustment has beenmade;

Heretofore metallic shields have been interposed between the operatorand said circuits in an effort to screen the latter; but'have usuallyproved to be either too complicated or insufiicient.

In the practice of my-invention with such a transmitter or receiver, thederangement of function that might be caused by the presence. of, ahuman body is prevented by controling the electric potential of thecarrier wave adjacent said apparatus. Thisresult is obtainedthrough aconnection to ground by way'of .a suitable .elec- 'tric conductor of alength bearingia definite relation to the length of the carrier wave.This conductor will be fixed to a point near the apparatus, and itslength will be such that a node of potential exists at said point. i Theoutside potential of the apparatus within a considerable radius aboutsaid point is thus rendered subconductor will be attached.

Hence the high frequency potential of the shield with reference toground, at least in'ithe vicinity of the end of said conductonsisvirtually nil; and the operator may approach as he likes conductor 4 isjoinedto the member 3 will be at without disturbing the apparatus in thesmallest degree. f v

The nature and advantages of the invention will more fully appear fromthe following description, taken with the drawing; that illustrates apreferred'construction in which the invention is embodied. Thisdisclosure, however, is illustraadvantage in connection with atransmitter. In either event, the apparatus will be screened by ber orshield 3 will be united to, a conductor 4,

tive only, and I may varyidetails ofshape, size, arrangeinent of parts,or mode of proceeding to the full extent indicatedlby the broad andgeneral meanings of the terms in which the appended claims areexpressed.

On the drawing:

Figure l is a diagrammatic view showing an ap paratus'for signaling.byrrafdio according to. my invention. 4 I

Figures 2, 3 and 4 present modifications thereof; a r j g The samecharacters of referenceidentify the I same. parts throughout. I

- In the particular description of what the drawing presents, thenumeral ;1 is employed to indi- 7 cate an antennaand the numeral 2 andassen1- blage of electrical parts operatively associated withtheantenna'l. Thisassemblage maybe of any well known design to work onrelatively willbe originated in the apparatus 2 and transferred to theantenna 1. For purposes of this disclosure the apparatus 2 may beregarded as a receiver, but the invention will operate with equal ametal member or shield-=3 in front, so that it will be between. theapparatus-and the operator,

who adjusts the parts 2. At one point the memtheopposite end of which isconnected to ground as shown at 5. V 7

When the apparatus 2 is in operation at high frequency and oscillationsare being received by the antennazl at high frequency, the presence ofthe body of the operator will interfere with the frequency adjustmentsto a marked extent.- I have found thatthis disturbing influence can becounteracted entirely by means of the grounded: conductor 4,providedthis conductor has a length bearing a definiterelation to thelength. of the carrier wave. Forinstance, substantially one-half awavelength answers my purpose, because under such conditions the pointwhere the zero potential with reference to'ground; and-so mum potential;and for that reason the body of the conductor between the shield 3 andground 5 should be so disposedthat it cannot be ap- 4 o I plates 11and'll', this battery being J'oinedfto one terminal of the battery 16and having'its op- I to the shield 3. This end may be attained, for

or I

- example, by bending. the conductor as indicated in Fig. I, andarranging it so that it extends beneath the apparatus ,2 and towards theback placing the body'of the conductor 4 sothat it will be out oftheway. If desired this conductor .may have a length which 'isjgreaterthan half; a wave length, such as. a length equalto one,- or one andone-half times the length. of the carrier wave, or in fact any odd.oreven multiple of one-half a'wave length, so long asit is con nectedand arrangedas described above.

In series with the antenna 1 will usual adjustable condenser 6, which isalso in series with the inductance coil '7; the ,latter l, having oneterminal joined to the gridS of a thermionic tube, with the otherterminal joinedto.

the cathode 9 of thistube. Bridged across'the leads connecting the twoterminals er the coil 7' 'to thegrid 8 and the cathode 9 is anadjustable Condenser 10.- -The plate of the tube is shown at 11 and thisplate is connected by'means of a suit-' able conductor to one end of-aregenerator coil 12, inductively associated with coil 7. The oppo'siteend of the coil 12 isconnected to one pole. 'of an adjustable condenser'13, having its opposite terminal. attached to the lead between the coil'7 and-the filamenti).

The plate 11 is also in series'with a radio frequency' choke coil'14,whichisc'onnected to one end of the primary of an audioffrequencytransformer 15. ,One terminal of the secondary of heatedcathode 9' andplate 11'. At 16 is the bat- "tery'for heating the'cathode 9 andsuitable conf "du'ctors connect the cathode 9" in parallel with thecathode 9. I also provide a battery 17 for the posite pole connected bymeans of'a conductor '19 to the-plate 11". In the'line ofthe conductor19 isa telephone 20. Of 'course the number of tubes, as regards theprinciple of this invention,- is

immaterial. As shown in Fig. L'theantenna may be grounded by having oneend of the coil of these two batte'ries- Radio frequency choke coils 18are included in the conductors leading iromthe battery 16 to'the cathode'9 andin the adjacent-part of the conductor 19; to isolate the twogrounded conductors land 4A fromeach I "other, if they are 'not jalreadyelectrically separated. The batteries needj-notnecessarily be -behindthe shield -3. The terminal of the primary of the transformer 15 remotefrom the coil l l may be united to the conductor 19; and the terminal ofthe secondary not joined to the grid 8 maybe united to one of the leadsbetweenthe filaments 9 and 9'.

In practice,-the-effect of. conductor 4 is to es tablish a potentialnode onthe' plate 3 in the vicinity of the point to which the conductor4 is attached. The point of attachment of thecOnductor eshown at 22ispreferably at the side or end of thepanel adjacent the adjustableparts of the circuits comprising the condensers 6; 10, 13,

this being the placefwhere the radio frequency oscillations mostlyoccur.With the conductor 4 r be the "united to -the point 22.

conductor islikewiseany odd or even proached by the operator whenhe isin proximity 7 so connected, the operator may approach the.

. panel 3 at any time and the body capacity, due to the presence of theoperator, will have no disturbing effect. He mayeven touch the panel 3 lnear the point '22 with'his fingers. It is imthereof away from theshield 3 or by otherwise pertant however, that thegreater portions ofthe conductors 4. and 4A between the attached and grounded ends beremoved as much as possuming these to be half a wave in length, has amaximum potential because a potential loop ex- ;yists thereat; anddisturbances would follow if the bodyvof either wire between the twoends thereof 96 were locatedat some point where it would be closeto theoperator when the latter adjusts any [part of the apparatus 2..

Figure 2 shows a modification wherein the antenna 1 has a separateground 23 and is not Figure 3 shows a grounded wire such as d'con-'taining an adjustable ."inductance 24, the total effective length ofthis wirealso being anyodd or even multipl'e of ,one-half a wave length.

Similarly; Figure l shows grounded conductor 4 with an adjustablecondenser 25 inthe line thereof, and the effective electrical length-ofthis multiple of u one-halfawavelength. 1%

With the inductance and capacity presen'tjthe actual length of i theconductors '4" can be shortened if 'thereis a scarcity ofavailable'space; and by making these elements adjustable, the desired 7effects can be obtained with 7 different wave Jill lengths for thereceiver or transmitter.

As described above in connection with, 1, the, body of the conductorv lin either Figures 3 or 4 must be so disposed that it cannot beappreached by the operator and is preferably putllb' beneath the panel 3and to the rear thereof.

1 Radio frequency choke coils may also be utilized in the connectionsfor the telephone 20. The arrangement or circuits shown is "intended tobe 1'01" example only, and may be varied withinlwide limits. i a

'The part of the shield 3 where the conductor 4 is-jolned is atsubstantially ground potential;

which is'virtually zero. Hence. external capacity adjacent this part ofthe shielddoes not afiect 'l25 i the apparatus 2at all; Some potentialmay exist "at the oppositezend; of the shield, but this ereates no"difiiculty because even there the potential can be kept at a low valueand the operator in making adjustments will stand eloseto the end wherethe wire 4 is attached.

With this device, thedisturbing effect of ex-;

ternalcapacity, due to'thepresence of the operator,aor in factexternal'capacity of any kind, ,is entirely; counteracted; and thisscheme works just as well'on a transmittingcircuit asupon a rec'eivingcircuit. 'To gain my end it is only necessary to connect a groundedconductor as set forth, and by this simple and inexpensive dimension thestable operation -is-assured.-

Having described myinvention, what I be-- have to be new and desire tosecure and protect by Letters Patent of the United States is:

1. A device for preventing external electrostatic capacity fromdisturbing radio signaling means including an antenna and apparatusbetween which and the antenna electrical oscillationsaretransferred, ashield forsaid apparatus, said antenna and said apparatuscomprisingadadjacent one end of said shield, and a conductor connectedto said end of said shield and being grounded, the conductor having alength equal to a multiple of a half wave length of said oscillationsand having the greater portion of its length disposed as far as possiblefrom said apparatus.

2. A device for preventing external electrostatic capacity fromdisturbing. radio signaling means including an antenna and apparatusbetween which and the antenna oscillations of high frequency aretransferred, said apparatus comprising a thermionic tube having acathode and an anode, means for supplying said cathode and anode withelectrical energy, and means for connecting said supplying means toground, said connecting means comprising a conductor having a lengthequal to a multiple of a half wave length of said oscillations, with thebody of the said conductor arranged to be remote from said apparatus.

3. A device for preventing external electrostatic capacity fromdisturbing radio signaling means including an antenna and apparatusbetween which and the antenna electrical oscillations of high frequencyare transferred, said apparatus containing adjustable elements for radiofrequency oscillations, a shield for said apparatus, means comprising aconductorconnected to said shield and to ground and having a lengthequal to a multiple of a half wave length of said oscillations, the bodyof said conductor being comparatively remote from said apparatus andsaid shield, said apparatus comprising a'thermionic tube containingcathode and anode, means for supplying electric energy to said cathodeand anode, choke coils between said supply means and said tube, andmeans for grounding the supply means by a conductor having an effectivelength equal to a multiple of a half wave length of said oscillations.

4. A device for preventing external electrostatic capacity fromdisturbing'radio signaling means including an antenna and apparatusbetween which and the antenna oscillations of high frequency aretransferred, said apparatus having thermionic tubes, meansfor supplyingelectrical energy to said tubes, and a shield before said apparatus,said device consisting of conductors connected to ground at one end andseparately to said supply means and said shield at their opposite endsand having an effective length equal to a multiple of a half wave lengthof said oscillations.

5. A device for preventing external electrostatic capacity fromdisturbing radio signaling means including an antenna and apparatusbetween which and the antenna electrical oscillations of high frequencyare transferred, said device comprising a shield in front'of saidapparatus and a conductor connected to ground at one end and to theshield at the other, and of a length to impose onthe shield in thevicinity ,of its point of connection therewith a potential node at thefrequency of said oscillations.

6. A device for preventing external electrostatic capacity fromdisturbing radio signaling means including an antenna and apparatusbetween which and the antenna electrical oscillations of high frequencyare transferred, said apparatus comprising a thermionic tube, means forsupplying electrical energy thereto, and a grounded conductorconnectedto said means, said conductor having a length bearing a definiterelation to the wave length of said oscillations, and bearing apotential node at its point of connection with said means.

7. The device according to claim 6, wherein radio frequency choke coilsare interposed between said apparatus and said means.

8. The method of avoiding body capacity effects in a radio signalingdevice including a shield and a ground connection therefor whichconsists in adjusting the inductance of the ground connection accordingto the signal frequency to produce a voltage node at the shield, therebyrendering said signaling device substantially nonresponsive to theeifects of body capacity.

9. A device for preventing external electrostatic capacity fromdisturbing radio signaling apparatus, comprising a shield for theaparatus, and a ground connection therefor of such length as wouldproduce a voltage node on the shield at the frequency of the signalingwave.

10 In a radio signaling device, an antenna member, tuning meanstherefor, a detector device associated therewith, control means for saidtuning means, a shield between said tuning means and said controldevice, and a ground connection for said shield having a length andinductance such as to produce a voltage node on said shield at thefrequency of the signaling wave.

JAMES O. WATKINS.

